Pitt Biologist Is Brilliant

PITTSBURGH—For the 14th year, Popular Science magazine has named its Brilliant 10, honoring the brightest young minds in science and engineering. University of Pittsburgh biologist Jonathan Pruitt has made the cut.

They’re networking cars, decoding the brain, preventing plagues—and, in the case of the Pitt’s Pruitt, using spider societies to explain evolution, providing the first proof that individuals in the wild sometimes sacrifice their own genetic survival for the sake of the group—a topic of hot contention among biologists for 40 years.

“It's a simultaneously startling and exciting experience to be listed among this year's Brilliant 10,” Pruitt says. “To know that our work has been able to pique the interest of such an audience is a dream come true. Our work on societal demise and the role this plays in evolution is very exciting to us and controversial in our discipline. We're merely excited by the opportunity to share this research with the public. I suspect people would be startled to know how much spider societies resemble our own.” 

Popular Science staffers combed through hundreds of nomination forms, looking for 10 scientists who have made a groundbreaking contribution to their fields since January 2014. 

Pruitt, an assistant professor of behavioral ecology in the University of Pittsburgh’s Department of Biological Sciences within the Kenneth P. Dietrich School of Arts and Sciences, became the first to empirically demonstrate “group selection” acting in the wild, publishing in the prestigious journal Nature.

The notion of “group selection”—that members of social species exhibit individual behavioral traits that render a population more or less fit for survival—has been bandied about in evolutionary biology since Darwin. The essence of the argument against the theory is that it’s a “fuzzy” concept without the precision of gene-based selection. 

Pruitt says that the theory of group selection argues that competition among groups should be a potent force in the evolution of animal societies, ranging from insects to humans and everything in between. While to a layperson this makes perfect sense (for instance, imagine all the ways that intertribal conflicts or wars among nations have influenced human society), in evolutionary biology, the concept of group selection has been one of the most contentious topics in the field. Pruitt used a rare kind of animal society, a social spider, to experimentally demonstrate that the rise and fall of societies is contingent on their ability to exhibit the perfect behavioral mix. Female social spiders exhibit one of two behavior types, either a “docile” or an “aggressive” type.

One can think of these like the animal analog of human personality. Pruitt’s work demonstrated that the ratio of docile to aggressive females is a major determinant of colony success and different environments call for different mixtures. Some environments call for more docile females, and other environments call for more aggressive females. Colonies that exhibit the wrong mixture collapse.

However, with the proper mixture, colonies flourish and quadruple in size. Never before has anyone demonstrated such dire consequences of group composition in any animal. This finding alone would be notable, but things don’t stop there. Pruitt demonstrated that societies have evolved the ability to maintain their optimal mixtures. When the mixtures of societies were experimentally altered, Pruitt demonstrated that societies can remedy their ailing mixtures by individuals’ selectively halting their reproductive output: whichever personality type is overabundant decreases (or ceases) reproduction. Pruitt’s work further provides evidence that the mechanisms colonies use to regulate their mixtures are genetically determined. In other words, group selection caused colonies to evolve mechanisms to maintain the perfect mix. 

Pruitt’s not just a scientist; he plays the steel drums and is an Eagle Scout, a former competitive chess player, a Disney snow-globe collector, and a notoriously fast talker. He adds, “I spend three months each year living in a hut in Africa—in Kalahari Desert. How’s that for bizarre?”

View the full article in the October issue of Popular Science, or at http://www.popsci.com/tags/2015-brilliant-10.

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9/22/15/klf/jm